# Homework Help: Energy to put space shuttle in orbit

1. Apr 7, 2009

### calculator20

1. The problem statement, all variables and given/known data
The space shuttle orbits about 300km above the surface of the Earth. The shape of the orbit is circular and the mass of the space shuttle is 6.8*104kg. The mass of the earth is 6.0*1024kg and the radius of the earth is 6.4 *106m. Calculate the energy needed to put the space shuttle into orbit.

2. Relevant equations

KE=GMm/rp

3. The attempt at a solution
Using G=6.67*10-11 with the mass of the earth and shuttle and the radius of the earth gives 4.2*1012J but the answer should be 2.2*1012J according to the book. Where am I going wrong?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Apr 7, 2009

### Astronuc

Staff Emeritus
Think about what the gravitational potential energy GMm/r means.

The shuttle lifts (or rises) from re to re+300 km, where re is the radius of the earth.

3. Apr 7, 2009

### tiny-tim

oops!

Hi calculator20!
erm … you can't just leave it there … it'll crash!

try giving it a shove!

4. Apr 7, 2009

### calculator20

If I do GMm/re I get 4.2*10 to the 12, GMm/re + 300000 gives 4.06 * 10 to the 12. The difference between them isn't 2.2 *10 to the 12?
I get

5. Apr 12, 2009

### yesyesyes

i am having exactly the same difficulty, its frustrating the hell out of me.
either i am not seeing something or there is an error in the answer page

6. Apr 12, 2009

### LowlyPion

Welcome to PF.

They want the total energy.

What is total energy to move from the surface of Terra to a 300km height?

What must the object have to be in orbit?

Etotal = ΔKE + ΔPE

7. Apr 12, 2009

### yesyesyes

so basically 2.2= KE (4.2) - PE (2.1)
allowing for roundings
?

Thanks a lot x